The present invention relates to rapidly curing compounds based on silane-modified polymers.
Silane-modified polymers represent a more recent development in the field of sealants. They extend the range of these materials, which include chemically reactive compounds such as silicones, polyurethanes and polysulfides as well as chemically non-reactive compounds such as butyl sealing materials, solvent-containing sealing materials and dispersion sealing materials. For sealing a joint or an aperture, sealing materials must meet a plurality of requirements and particularly they must have good adhesive properties with respect to the flanks of the joint or to the substrates. For this purpose, they should normally be elastic in order to compensate spatial changes of the joint occurring as a result of temperature changes. Also compatibility with the substrates must be guaranteed.
Silane-modified polymers are cold vulcanized one- or two-component compounds. These are polymers such as polyether or polyurethanes containing silane end groups that cross-link into rubber-like elastic or plasto-elastic materials under absorption of water at room temperature. In one-component systems, the water usually comes from the atmosphere. During the chain elongation or cross-linking reaction, alcohol is separated from the silane end groups, namely methanol or ethanol in the most widely spread methoxy or ethoxy end groups. After curing, the products are characterized by good self-adhesion to the most different material surfaces and by a generally good resistance to the influences of temperature, light, atmosphere, moisture and chemicals.
The curing of one-component compounds that will cross-link under the absorption of moisture at room temperature runs comparatively slowly because the water necessary for the reaction is required to diffuse from the surrounding atmosphere into the interior of the compound. The curing speed therefore decreases with a proceeding reaction in the interior of the compound. At a low air moisture or at an unfavorable surface-to-volume of compound ratio, the reaction can become very slow or can even completely come to a standstill in steam-tight closed rooms.
Although such atmospheric moisture-hardening silane-modified polymer compounds can be normally used in a wide range, use thereof as adhesive or sealing materials is limited, particularly in the industrial production, due to their slow curing. If only slowly hardening compounds are used in industrial productions, short station times that are desired for economic reasons account for huge intermediate storage facilities required for reliably curing sealed or glued components. Where necessary, these intermediate storage facilities must be additionally air-conditioned, humidified or ventilated. Thus high quantities are possibly produced already before a first-time examination of finished parts for freedom from defects and operational reliability is carried out. Large-area adhesive connections between diffusion-tight surfaces using atmospheric moisture-hardening compounds are feasible as little as the production of molded bodies in closed molds.
Also known are two-component compounds based on silane-modified polymers. One example is International patent application publication No. WO 2009/060199, which proposes such compounds as a sealing compound for insulating glass panes. Curing shall be achieved by the addition of a moist filling material, which is calcium carbonate in the examples. Even this system is not optimal in every respect.
From German Patent DE 69429565 it is known that hardening of α,ω-di(hydroxy)diorganopolysiloxane polymers in mixtures with different cross-linking agents, filling materials, plasticizers etc. can be accelerated if mixed with an aqueous second component. As a substrate for water also Na2B4O7*10H2O, Na2HPO4*12H2O and Na2CO3*10H2O are mentioned in addition to zeolites and silica gel. Scarcely any example achieved curing in less than 24 hours.
International patent application publication No. WO 2010/131037 describes intumescent compositions that are applied as a coating to steel constructions for fire protection. The intumescent compositions consist of a first component from alkoxysilane-terminated polyethers or polyurethanes, and a second component from plasticizers and intumescent additions/raw materials, an acid source, a carbon source and a gas source. The composition can be formulated both as a one-component and a two-component composition. Application thereof shall take place by spraying so that the composition is not suitable as a sealing or adhesive material from the aspect of viscosity.
It would be expedient to have a system in which the mixing ratio between the components can be varied in vast ranges in order to obtain even better mechanical properties and adhesive properties. Further, it would be desirable to be able to observe the effectiveness of the mixing of the components through different colors of both components. Moreover, the components should be formulated in such a manner that the viscosities are similar or matched in order to facilitate good intermixture of both components. Also the adjustment of the residual moisture of the raw materials, particularly of the filling materials, is complicated and it would be desirable to have a system in which curing is independent of the residual moisture. It would also be expedient to have a system which can be formulated solvent-free (environmental safety, operational safety) and/or silicone-free (compatibility with substrates).